Aid worker Helen Johnston, seen in this undated family photograph released by Britain's Foreign and Commonwealth Office, was rescued from her Taliban captors Saturday.

By msnbc.com staff and news services

A NATO rescue team dropped by helicopter in remote mountains of northern Afghanistan early on Saturday freed four aid workers, including two doctors, who had been seized by the Taliban last month, the alliance said.

The aid workers, employed by Swiss-based Medair, were en route to flood-stricken parts of Badakhshan province when they were kidnapped.

NATO forces entered the area under cover of darkness and after confirming the presence of the hostages, carried out a successful raid to free them, Lieutenant Commander Brian Badura, a spokesman for the NATO-led International Security Assistance Force (ISAF) told Reuters.

The rescue team suffered no casualties in the operation, Badura said. The kidnappers were armed with heavy machine guns, AK-47 assault rifles, and rocket-propelled grenades.

Shamsul Rahman Shams, the deputy governor of Badakhshan, said five men who were holding the aid workers were killed in the operation.

"It was an extraordinarily brave, breathtaking even, operation that our troops had to carry out," U.K. Prime Minister David Cameron said, according to BBC News. "I pay tribute to their skill and dedication."

The alliance identified the two foreigners freed as Helen Johnston and Moragwe Oirere, who along with two Afghans worked for Medair, a humanitarian non-governmental organization based near Lausanne, Switzerland.

The aid workers had been travelling by donkey to visit a clinic in the remote Yawan district, where the road had been destroyed by floods caused by melting snow after one of the worst Afghan winters in decades.

Afghan forces have taken over security in the provincial capital Faizabad and some parts of Badakhshan ahead of the Western drawdown.

Afghan authorities originally said five people had been kidnapped, but it later emerged that one of the party managed to escape from the hostage takers.

The kidnapping of foreigners has become relatively common in parts of Afghanistan since U.S-backed Afghan forces toppled the Taliban government in 2001, heralding a 11-year anti-insurgent war.

In 2010, 10 foreign medical workers, including six Americans, were killed in Badakhshan in an attack blamed on insurgents.

Other attacks have been blamed on criminal groups looking for ransom. Police in Badakhshan earlier said the kidnappers in this case were demanding money, and they appeared to be members of a criminal gang.